Special Weather Statement, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
1045 AM EDT Wed Apr 5 2017

.UPDATE...
The AVIATION Section has been updated below.

&&

.SYNOPSIS...
Issued at 305 AM EDT Wed Apr 5 2017

A particularly active day and evening can be expected across Central
Indiana as a low pressure system tracks from the Central Plains into
the Lower Midwest.  Severe thunderstorms will be possible this
afternoon and evening, especially over the southern portions of the
forecast area.  Tonight, the thunderstorm threat will end, but rain
showers will persist and continue through tomorrow.  Strong winds on
Thursday with gusts up to 50 mph and temperatures only in the 40s
will result in a blustery day.  As temperatures drop further on
Thursday night, a few snow showers could even mix in with the rain
showers.  Precipitation will be out of the area completely by Friday
though, and dry conditions will prevail through Sunday.  However,
the cool temperatures and clear skies could result in frost
potential Friday night.  Further out, shower and thunderstorm
chances will return Sunday night through early next week with
another system. This one will take a more northerly route.

&&

.NEAR TERM /Today and Tonight/...

Issued at 305 AM EDT Wed Apr 5 2017

The main focus of the near term period will be the severe threat
this afternoon and evening as a low pressure system moves in from
the Missouri Valley. Latest Day 1 convective outlook continues to
have the highest threat focused south of I-70 with an enhanced
risk. The remainder of the forecast area falls under a slight and
marginal risk.

MAIN THREATS: Isolated tornadoes, damaging winds, large hail,
frequent lightning, heavy downpours.

TIMING: Wed 18Z-03Z, this is a moderate to high confidence time
frame. Initial convection is progged to start across the western
counties as early as this morning. However, best dynamics point
toward highest severe potential escalating in the Wed 20Z-01Z time
frame.

Showers and thunderstorms are expected to start forming along and
ahead of an associated warm front this morning. By Wed 18Z,
surface low is expected to be centered over southern Illinois with
large vort max associated with 100+ upper level jet stretching
from southern Illinois to northeast Texas. Vort max is progged to
track across the forecast area between Wed 00Z and Thu 06Z with
convective initiation ahead of it. MU Cape values of 500-1000 J/kg
and LI's in the -3 to -4 range will be focused over those southern
counties as mentioned above where temperatures will also be in the
low to mid 70s (mainly pinpointing the southeast corner).

As surface low shifts east of the area after Thu 06Z,
thunderstorms will quickly taper off with only rain showers
driven by the upper low. The northwestern counties will be
impacted by rain the longest with possible flash flooding
implications by tonight.

Much cooler air will filter in behind the system as northwest winds
quickly increase behind the aforementioned low tonight. Overnight
lows will drop into the mid to upper 30s with northwest winds of
10 to 15 mph, gusting to 30 mph after midnight.

&&

.SHORT TERM /Thursday through Friday Night/...

Issued at 305 AM EDT Wed Apr 5 2017

The main focus of the short term period will be the high winds on
Thursday on the back side of the aforementioned low pressure system
as pressure gradient tightens.  Winds will be out of the northwest
with sustained speeds of 15 to 30 mph, gusting as high as 50 mph at
times.  After collaboration, will continue to hold off on an
advisory at this point, but one will most likely be needed with
future forecast issuances.

The other area of focus will be the below normal temperatures on
Thursday and Friday nights as lows dip into the low to mid 30s. This
will mean the potential for snow showers to mix in with any
lingering rain showers on Thursday night, and then the threat of
frost for Friday night as skies become clear.  As far as high
temperatures, Thursday will be chilly with highs only topping off in
the 40s.  Friday, the weak return to a warming trend will commence
with highs slowly creeping back into the low to mid 50s.  Latest
superblend initialization looks reasonable, so will not deviate from
those numbers at this time.

Otherwise, conditions will be dry across the entire forecast area by
Friday.  Any lingering precipitation with the trailing upper low
will end from west to east on Thursday night.

&&

.LONG TERM (Saturday through Tuesday)...

Issued at 158 AM EDT Wed Apr 5 2017

With strong agreement between the underlying models, confidence is
high the regional blend should be a good forecast through Monday
night. Most temperature errors will be 2 degrees or less. POPs
should accurately reflect a dry weekend, with increasing rain
chances later.

Forecast uncertainty increases Tuesday. The GFS and European models
differ in handling of an approaching system aloft. There is no
reason to alter the regional blend, but the forecast issued today
could change a lot in updates.

&&

.AVIATION /Update for KIND TAF/...

Issued at 1039 AM EDT Wed Apr 5 2017

Winds currently light and variable as a result of recent shower
passage and either surface trough or weak surface flow in the
area. Winds should re-establish towards forecast values within
next hour or two, or by 1600z.

Brief deck around 2000 feet right now is shower related and should
scatter out soon. Satellite trends indicate a break into sunshine
by or before 1600z which should further re-establish stronger and
gustier wind forecast.

Cluster of storms west of Vincennes should track west of KIND but
perhaps in vicinity between 1600-1700z.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SYNOPSIS...TDUD
NEAR TERM...TDUD
SHORT TERM...TDUD
LONG TERM....JK
AVIATION...Tucek

Hazardous Weather Outlook
National Weather Service Indianapolis IN
511 AM EDT Wed Apr 5 2017

INZ021-028>031-035>049-051>057-060>065-067>072-060915-
Carroll-Warren-Tippecanoe-Clinton-Howard-Fountain-Montgomery-Boone-
Tipton-Hamilton-Madison-Delaware-Randolph-Vermillion-Parke-Putnam-
Hendricks-Marion-Hancock-Henry-Vigo-Clay-Owen-Morgan-Johnson-Shelby-
Rush-Sullivan-Greene-Monroe-Brown-Bartholomew-Decatur-Knox-Daviess-
Martin-Lawrence-Jackson-Jennings-
Including the cities of Lafayette, Frankfort, Kokomo,
Crawfordsville, Anderson, Muncie, Indianapolis, Terre Haute,
Shelbyville, Bloomington, Columbus, Vincennes, Bedford, and Seymour
511 AM EDT Wed Apr 5 2017

This hazardous weather outlook is for central Indiana.

.DAY ONE...Today and Tonight.

Outlook: Severe thunderstorms possible, with the risk increasing from
north to south.

Hazards: Tornadoes. Damaging straight line winds. Large hail.
Lightning. Heavy rain.

Timing: Severe weather possible from this afternoon through early
tonight with the highest chance 5 PM to 10 PM.

Discussion: A complex system composed of a low pressure center, a
warm front, and a cold front will cross Indiana.

 .DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Outlook: Very windy Thursday. Snow showers possible Thursday night,
but no accumulation expected. Areas of frost Friday night. Chance of
thunderstorms Monday and Tuesday, but it is too early to tell if
storms will be severe.

Discussion: Strong low pressure will dominate Indiana weather into
Thursday night, then give way to high pressure. Another low pressure
system should approach early next week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed this afternoon and evening.

&&

More information, along with other weather, hydrological and climate
information can be found at http://weather.gov/ind

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